TECHNICAL FIELD
[0001] This invention relates to a method for producing rare earth magnet by coating a sintered
magnet body with a rare earth compound-containing powder and heat treating for causing
the rare earth element to be absorbed in the sintered magnet body, wherein the rare
earth compound powder is efficiently coated and rare earth magnet having excellent
magnetic properties is efficiently produced; and a rare earth compound application
device suited for use in the rare earth magnet producing method.
BACKGROUND ART
[0002] Rare earth permanent magnets including Nd-Fe-B base magnets find an ever spreading
application owing to their excellent magnetic properties. Methods known in the art
for further improving the coercivity of these rare earth magnets include a method
for producing a rare earth permanent magnet by coating the surface of a sintered magnet
body with a rare earth compound powder, and heat treating the coated body for causing
the rare earth element to be absorbed and diffused in the sintered magnet body (Patent
Document 1:
JP-A 2007-053351, Patent Document 2:
WO 2006/043348). This method is successful in increasing coercivity while suppressing any decline
of remanence.
[0003] In the prior art, for coating the rare earth compound, methods of applying a slurry
of a rare earth compound-containing powder dispersed in water or organic solvent to
a sintered magnet body by immersing the magnet body in the slurry, or spraying the
slurry to the magnet body, to coat the magnet body with the slurry, and then drying
are generally employed. In the case of immersion coating, it is common in view of
productivity to adopt a net conveyor system wherein a plurality of sintered magnet
bodies are continuously conveyed and coated by means of a net conveyor.
[0004] That is, the net conveyor system includes a net conveyor
c as shown in FIG. 4. A plurality of sintered magnet bodies 1 are rested on the net
conveyor
c while they are spaced apart at predetermined intervals. The magnet bodies 1 are continuously
conveyed, passed through a coating tank
t filled with the slurry 2 in the course of conveyance, where they are immersed in
and coated with the slurry, withdrawn from the slurry 2, further conveyed while being
rested on the net conveyor
c, and passed through a drying zone 3 equipped with a layer-providing setup where they
are dried, i.e., the solvent in the slurry is removed. In this way, the rare earth
compound powder is coated.
[0005] However, the net conveyor system tends to give rise to problems that in the coating
steps including entry and immersion of sintered magnet bodies 1 in the slurry 2, and
withdrawn of sintered magnet bodies 1 from the slurry 2, the sintered magnet bodies
1 move on the conveyor to come in contact with each other, causing coating failures
on the contact surfaces, that the slurry tends to deposit or stick to the conveyor
system to invite mechanical failures, and that the slurry 2 is carried over outside
the coating tank
t by the conveyor belt, indicating that noble rare earth compound is consumed in waste.
There is also a problem that the system tends to occupy a large footprint because
the steps from slurry coating to drying are carried out while the sintered magnet
bodies are conveyed horizontally by the net conveyor.
[0006] Patent Document 3 describes formation of rare earth sintered magnets by slurry coating
of a magnet body, during which the magnet body is rotated, followed by heat treatment.
Patent Document 4 describes a rotating drum having multiple pockets for immersing
workpieces inserted in the pockets in a lubricant bath.
PRIOR ART DOCUMENTS
PATENT DOCUMENTS
SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0008] An object of the invention, which is made under the above circumstances, is to provide
a method for producing rare earth magnet comprising the steps of applying a slurry
of a powder in a solvent to the surface of a sintered magnet body of R
1-Fe-B composition (wherein R
1 is one or more elements selected from Y, Sc and rare earth elements), the powder
containing one or more compounds selected from an oxide, fluoride, oxyfluoride, hydroxide
and hydride of R
2 (wherein R
2 is one or more elements selected from Y, Sc and rare earth elements), drying the
slurry to coat the magnet body with the powder, and heat treating the coated magnet
body, the method being capable of applying the slurry uniformly and efficiently to
coat the powder uniformly and efficiently, while effectively suppressing the wasting
of the rare earth compound, and reducing the area of the system for carrying out the
coating steps; and a rare earth compound application device suited for use in the
rare earth magnet producing method.
MEANS FOR SOLVING THE PROBLEMS
[0009] To attain the above object, the invention provides a method for producing rare earth
magnet as defined below as [1] to [8].
- [1] A method for producing rare earth permanent magnet comprising the steps of applying
a slurry of a powder in a solvent to sintered magnet bodies of R1-Fe-B composition (wherein R1 is one or more elements selected from Y, Sc and rare earth elements), the powder
containing one or more compounds selected from an oxide, fluoride, oxyfluoride, hydroxide
and hydride of R2 (wherein R2 is one or more elements selected from Y, Sc and rare earth elements), drying the
slurry to coat the sintered magnet bodies with the powder, and heat treating the coated
bodies for causing R2 to be absorbed in the sintered magnet bodies, the method further comprising the steps
of:
providing a conveyor drum having a plurality of holding pockets circumferentially
arranged in its periphery,
rotating the conveyor drum while a portion of the drum is immersed in the slurry,
placing a sintered magnet body in one holding pocket at a predetermined position of
the drum prior to entry into the slurry, so that the sintered magnet body is held
in the holding pocket, the sintered magnet body being conveyed along the rotational
track of the conveyor drum, immersed in the slurry, then withdrawn from the slurry,
and conveyed further whereby the slurry is dried and the sintered magnet body is coated
with the powder,
recovering the sintered magnet body from the pocket at a predetermined position after
the drying treatment and prior to re-entry into the slurry, and
subjecting the sintered magnet body to the subsequent heat treatment.
- [2] The rare earth magnet producing method of [1] wherein the holding pocket is a
pocket of circular bore shape axially extending throughout the conveyor drum, an uncoated
sintered magnet body is inserted into the pocket from one side surface of the conveyor
drum, a coated sintered magnet body, which has been accommodated in the pocket, is
displaced by the uncoated sintered magnet body to the other side surface of the conveyor
drum, for thereby recovering the coated sintered magnet body from the pocket, whereby
supply and recovery of sintered magnet bodies are simultaneously performed.
- [3] The rare earth magnet producing method of [2] wherein a plurality of conveyor
drums are juxtaposed with their side surfaces closely opposed, the powder coating
process is carried out on each conveyor drum, the sintered magnet body is inserted
into the holding pocket in one drum, and at the same time, the sintered magnet body,
which has been accommodated in the pocket, is displaced into the pocket in another
drum and accommodated therein, whereby the coating process from slurry immersion to
drying is repeated plural times.
- [4] The rare earth magnet producing method of any one of [1] to [3] wherein the sintered
magnet body supplied into the holding pocket is recovered after the conveyor drum
is rotated plural turns, whereby the coating process from slurry immersion to drying
is repeated plural times.
- [5] The rare earth magnet producing method of any one of [1] to [4] wherein the conveyor
drum has a main body composed of a frame and a mesh metal or punching metal.
- [6] The rare earth magnet producing method of any one of [1] to [5] wherein the step
of drying the sintered magnet body which is withdrawn from the slurry and conveyed
further includes blowing air thereto.
- [7] The rare earth magnet producing method of [6] wherein the drying step includes
injecting air at a temperature within the boiling point (TB) of the solvent in the slurry ±50°C to the sintered magnet body.
- [8] The rare earth magnet producing method of [6] or [7] wherein the drying step includes
injecting air to the sintered magnet body which is withdrawn from the slurry, for
thereby removing any residual droplets, and then injecting hot air thereto.
To attain the above object, the invention also provides a slurry application device
as defined below as [9] to [14].
- [9] A device for applying rare earth compound when rare earth permanent magnet is
produced by applying a slurry of a powder in a solvent to sintered magnet bodies of
R1-Fe-B composition (wherein R1 is one or more elements selected from Y, Sc and rare earth elements), the powder
containing one or more compounds selected from an oxide, fluoride, oxyfluoride, hydroxide
and hydride of R2 (wherein R2 is one or more elements selected from Y, Sc and rare earth elements), drying the
slurry to coat the sintered magnet bodies with the powder, and heat treating the coated
bodies for causing R2 to be absorbed in the sintered magnet bodies,
the device comprising
an applicator tank for containing the slurry,
a conveyor drum which rotates while a portion of the drum is immersed in the slurry,
a plurality of holding pockets circumferentially arranged in the periphery of the
conveyor drum, and
drying means for blowing air into the holding pocket for drying the sintered magnet
body accommodated in the pocket,
wherein a sintered magnet body is supplied into one holding pocket at a predetermined
position of the drum prior to entry into the slurry, the sintered magnet body held
in the pocket is conveyed along the rotational track of the conveyor drum, immersed
in the slurry, then withdrawn from the slurry, and dried by the drying means, and
the sintered magnet body is recovered from the pocket at a predetermined position
after the drying treatment and prior to re-entry into the slurry.
- [10] The rare earth compound application device of [9] wherein the conveyor drum has
a main body composed of a frame and a mesh metal or punching metal.
- [11] The rare earth compound application device of [9] or [10] wherein the drying
means is adapted to blow hot air into the holding pocket to dry the sintered magnet
body therein, the device further comprising droplet removing means for injecting air
to the sintered magnet body accommodated in the pocket for thereby removing any residual
droplets, prior to the drying treatment.
- [12] The rare earth compound application device of any one of [9] to [11] wherein
the holding pocket is a pocket of circular bore shape axially extending throughout
the conveyor drum, an uncoated sintered magnet body is inserted into the pocket from
one side surface of the conveyor drum, a coated sintered magnet body, which has been
accommodated in the pocket, is displaced by the uncoated sintered magnet body to the
other side surface of the conveyor drum, for thereby recovering the coated sintered
magnet body from the pocket.
- [13] The rare earth compound application device of [12] wherein a plurality of conveyor
drums are juxtaposed with their side surfaces closely opposed, the powder coating
process is carried out on each conveyor drum, the sintered magnet body is inserted
into the holding pocket in one drum, and at the same time, the sintered magnet body,
which has been accommodated in the pocket, is displaced into the pocket in another
drum and accommodated therein, whereby the coating process from slurry immersion to
drying is repeated plural times.
- [14] The rare earth compound application device of any one of [9] to [13] wherein
the sintered magnet body supplied into the holding pocket is recovered after the conveyor
drum is rotated plural turns, whereby the coating process from slurry immersion to
drying is repeated plural times.
[0010] That is, according to the producing method and application device of the invention,
as a conveyor drum rotates while being partly immersed in a slurry, sintered magnet
bodies are conveyed by the conveyor drum while being accommodated in holding pockets
arranged in the periphery of the conveyor drum, and in the course of conveyance, the
magnet bodies are passed through the slurry, coated therewith, and dried whereby the
sintered magnet bodies are surface coated with the powder.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0011] As mentioned above, sintered magnet bodies are conveyed by the conveyor drum while
being accommodated in holding pockets of the drum, coated with the slurry and dried.
Even when the coating step is carried out continuously on a plurality of sintered
magnet bodies, it is avoided that sintered magnet bodies come in contact with each
other so that coating failures occur at contact areas. The slurry is uniformly and
properly applied, and sintered magnet bodies are uniformly and efficiently coated
with the powder. Since the conveyor drum rotates while a portion thereof is immersed
in the slurry in the coating tank, the slurry carried over by the conveyor drum is
returned to the coating tank as a result of rotation of the drum, so that little of
the slurry is carried out of the coating tank. As compared with the net conveyor system,
the wasting of rare earth compound is effectively minimized. Furthermore, since the
conveyance track of sintered magnet bodies by the conveyor drum is a circular track
delineated above the coating tank by rotation of the conveyor drum, the system is
made compact to substantially reduce its footprint, as compared with the net conveyor
system entailing a horizontal conveyance track.
[0012] In addition, according to the producing method and application device of the invention,
the sintered magnet bodies are uniformly coated over the entire surface with the rare
earth compound powder and the coating step is carried out quite efficiently. Rare
earth magnet having improved magnetic properties including a fully increased coercivity
can be efficiently produced.
BRIEF DESCRIPTION OF THE DIAGRAMS
[0013]
[FIG. 1] FIG. 1 is a schematic view showing an application device in one embodiment
of the invention.
[FIG. 2] FIG. 2 is a schematic perspective view showing a conveyor drum in the application
device.
[FIG. 3] FIG. 3 is a schematic view showing a portion of the application device in
another embodiment of the invention.
[FIG. 4] FIG. 4 is a schematic view showing a prior art rare earth compound applying
system.
EMBODIMENT FOR CARRYING OUT THE INVENTION
[0014] As described above, the method for producing rare earth magnet according to the invention
includes the steps of applying a slurry of a powder in a solvent to sintered magnet
bodies of R
1-Fe-B composition (wherein R
1 is one or more elements selected from Y, Sc and rare earth elements), the powder
containing one or more compounds selected from an oxide, fluoride, oxyfluoride, hydroxide
and hydride of R
2 (wherein R
2 is one or more elements selected from Y, Sc and rare earth elements), drying the
slurry to coat the magnet bodies with the powder, and heat treating the coated magnet
bodies for causing R
2 to be absorbed in the magnet bodies.
[0015] The R
1-Fe-B sintered magnet body used herein may be one obtained by any well-known method.
For example, a sintered magnet body may be obtained by coarsely milling a mother alloy
containing R
1, Fe and B, finely pulverizing, compacting and sintering according to the standard
method. It is noted that R
1 is one or more elements selected from Y, Sc and rare earth elements, specifically
Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu.
[0016] According to the invention, the R
1-Fe-B sintered magnet body is shaped to a predetermined shape as by grinding, if necessary,
coated on its surface with a powder containing one or more compounds selected from
an oxide, fluoride, oxyfluoride, hydroxide and hydride of R
2, and heat treated for causing absorption and diffusion (grain boundary diffusion)
of R
2 into the sintered magnet body, thereby obtaining the desired rare earth magnet.
[0017] It is noted that R
2 is one or more elements selected from Y, Sc and rare earth elements, specifically
Y, Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu, like R
1 mentioned above. It is preferred, though not limited, that R
2 contain at least 10 at%, more preferably at least 20 at%, and even more preferably
at least 40 at% in total of Dy and/or Tb. It is more preferred in view of the object
of the invention that R
2 contain at least 10 at% of Dy and/or Tb and the total concentration of Nd and Pr
in R
2 be lower than the total concentration of Nd and Pr in R
1.
[0018] According to the invention, the powder is coated by dispersing the powder in a solvent
to prepare a slurry, applying the slurry to the surface of the sintered magnet body,
and drying. While the particle size of the powder is not particularly limited, a particle
size commonly employed as a rare earth compound powder used for absorptive diffusion
(grain boundary diffusion) may be selected, and specifically, an average particle
size of preferably up to 100 µm, more preferably up to 10 µm. The lower limit of particle
size is preferably at least 1 nm, though not limited. The average particle size may
be determined as a weight average value D
50 (i.e., particle size corresponding to a cumulative weight of 50 % or median diameter)
using a particle size distribution measuring system based on the laser diffraction
method or the like. The solvent in which the powder is dispersed may be water or an
organic solvent. Examples of the organic solvent include ethanol, acetone, methanol,
and isopropyl alcohol, but are not limited thereto. Inter alia, ethanol is preferably
used.
[0019] Although the amount of the powder dispersed in the slurry is not particularly limited,
a slurry having the powder dispersed in a dispersing amount of preferably at least
1 %, more preferably at least 10 %, even more preferably at least 20 % as mass fraction
is used in order to coat the powder effectively and efficiently. Since too much dispersing
amounts give rise to inconvenience such as failure to form a uniform dispersion, the
upper limit is preferably up to 70 %, more preferably up to 60 %, even more preferably
up to 50 % as mass fraction.
[0020] According to the invention, as the method of applying the slurry to the sintered
magnet body and drying to coat the surface of the magnet body with the powder, a method
of using a conveyor drum, conveying the sintered magnet body thereby, passing the
magnet body through the slurry, thereby immersing the magnet body in the slurry and
coating the magnet body with the slurry, and drying while further conveying the magnet
body by the conveyor drum is employed. Specifically, coating of the powder may be
carried out using the application device shown in FIGS. 1 and 2.
[0021] FIGS. 1 and 2 schematically illustrate a rare earth compound application device in
one embodiment of the invention. The application device includes a conveyor drum 4
adapted to rotate about a horizontal axis 41 by a rotational drive mechanism (not
shown). The conveyor drum 4 is positioned such that a portion thereof is immersed
in a slurry 2 contained in a coating tank (not shown). In FIG. 1, a portion of the
drum corresponding to 4 to 8 o'clock on the clock dial is immersed in the slurry 2.
While the range of immersion in the slurry 2 is not limited to the range shown in
FIG. 1, the setup may be such that at least one holding pocket 42 (to be described
later) at the lowest point is completely immersed in the slurry 2 and the horizontal
axis 41 is located above the surface of the slurry 2. It is noted that although the
conveyor drum 4 is adapted to rotate about the horizontal axis 41 in the illustrated
embodiment, the rotational axis of the conveyor drum need not necessarily be a horizontal
axis, as long as the conveyor drum rotates while a portion of the drum is necessarily
immersed in the slurry, and the sintered magnet body held by the conveyor drum is
once completely immersed in the slurry and withdrawn from the slurry in accordance
with rotation of the drum.
[0022] The conveyor drum 4 is provided with a plurality of (twelve in the figure) holding
pockets 42 which are circumferentially arranged in a row and at an equal spacing.
As the drum 4 rotates with the sintered magnet bodies 1 accommodated and held in the
holding pockets 42, the sintered magnet bodies 1 are conveyed along a circular track.
The holding pockets 41 are pockets of circular bore shape axially extending throughout
the drum and are open at both side surfaces of the drum.
[0023] The size of the holding pocket 42 may be set as appropriate depending on the size
and shape of the sintered magnet body 1 to be accommodated therein. Although the size
is not particularly limited, the diameter of the holding pocket 42 is preferably equal
to the maximum diameter in cross section of the sintered magnet body 1 (maximum diagonal
in case of rectangular shape) plus about 1 to 2 mm. This setting ensures that the
sintered magnet body 1 is smoothly inserted and removed and the sintered magnet body
1 accommodated in the holding pocket 42 is conveyed in a steady manner without substantial
movement within the pocket 42. The depth of the holding pocket 42 may be set as appropriate
depending on the size of the sintered magnet body 1 and is generally at least 50 %,
preferably about 70 to 90 % of the length of the sintered magnet body 1. Furthermore,
the spacing between holding pockets 42 is preferably at least 10%, more preferably
at least 30 % of the diameter of the pocket. Since too large a spacing can detract
from productivity, the spacing is preferably up to 100 % of the pocket diameter.
[0024] As the conveyor drum 4 rotates, each holding pocket 42 enters the slurry 2 whereupon
the slurry 2 flows into the holding pocket 42 from the openings at both ends, whereby
the sintered magnet body 1 accommodated in the holding pocket 42 is immersed in the
slurry. At least the main body of the conveyor drum 4 provided with the holding pockets
42 is preferably composed of a frame (not shown) and a mesh metal or punching metal
in order that the slurry 2 flow into the pocket 42 and the sintered magnet body 1
accommodated in the pocket 42 be immersed in the slurry.
[0025] When the main body of the conveyor drum 4 is formed using a mesh metal or punching
metal, the sintered magnet body 1 is effectively immersed in the slurry 2, and the
amount of the slurry carried over by rotation of the conveyor drum 4 is reduced. This
enables stable slurry coating. The efficiency of drying is increased during the drying
step to be described later. The opening of the mesh metal or punching metal is preferably
at least 1 mm so that the slurry 2 and drying air effectively flow therethrough. The
upper limit is arbitrary as long as the sintered magnet body 1 is held in a stable
manner.
[0026] As the conveyor drum 4 having the sintered magnet bodies 1 accommodated in the holding
pockets 42 rotates clockwise as viewed in the figure, the sintered magnet bodies 1
are conveyed. Although the rotational speed of the conveyor drum 4 is not particularly
limited, the rotational speed is set depending on the diameter of the drum, preferably
so as to give a circumferential speed of 200 to 2,000 mm/min, more preferably 400
to 1,200 mm/min at the position where the holding pockets 42 are formed. If the circumferential
speed, i.e., conveying speed is less than 200 mm/min, it is difficult to attain an
industrially acceptable throughput. If the circumferential speed exceeds 2,000 mm/min,
there may be inconvenience that short drying often occurs during treatment in a drying
zone 3 to be described later, the size of a blower or the number of blowers must be
increased in order to ensure drying, and the drying zone 3 must be scaled up. It is
noted that although the rotation of the conveyor drum 4 may be continuous or intermittent,
intermittent rotation is preferable when the efficiency of replacement operation of
sintered magnet bodies 1 to be described later is taken into account.
[0027] As shown in FIG. 1, a range of the conveyor drum corresponding to 9 to 2 o'clock
on the clock dial (range shown by arrow 3 in FIG. 1) is a drying zone 3. A drying
means for blowing air to the holding pockets 42 is provided in this range. The air
blow by the drying means may be hot air blow or normal temperature air blow. The temperature
of air blow may be adjusted as appropriate depending on the drying time (conveying
speed and length of drying zone), the size and shape of sintered magnet bodies, the
concentration and coating weight of the slurry, and the like. Although the air blow
temperature is not particularly limited, it is preferably in a range of the boiling
point (T
B) of the slurry solvent ±50°C. When water is used as the solvent, for example, the
temperature of hot air blow may be adjusted in a range of 40°C to 150°C, preferably
60°C to 100°C.
[0028] Now, in a first half portion of the drying zone 3, for example, in a range of the
conveyor drum 4 corresponding to 9 to 10:30 o'clock on the clock dial, a residual
droplet removing means (not shown) of injecting air may be set as a residual droplet
removal section. Then the residual droplet removal section acts to inject air to the
sintered magnet body 1 to remove any residual slurry on the surface of the sintered
magnet body 1 before drying is carried out by blowing hot air as mentioned above.
The residual droplet removal section (residual droplet removing means) is not necessarily
essential. With the residual droplet removal section omitted, removal of residual
droplets may be carries out at the same time as drying by the drying means. If drying
is carried out with residual droplets remaining on the surface of sintered magnet
body, there is a likelihood of uneven coating of the powder. It is preferred in this
sense that residual droplets are fully removed by the residual droplet removal section
(residual droplet removing means) before drying is carried out. In some cases, in
order to accelerate drying, the air blow injected by the residual droplet removing
means may also be hot air blow like that of the drying means.
[0029] The drying means and residual droplet removing means may be constructed by arranging
a plurality of air injection nozzles (not shown) outside the conveyor drum 4 and along
the circumference of the drum. Air or hot air is injected from the air injection nozzles
to carry out the drying or residual droplet removal. Herein, the shape, size and angle
(injection angle) of each nozzle may be set as appropriate depending on the size and
shape of sintered magnet bodies 1, the material (mesh metal or punching metal) of
the conveyor drum 4, and the like, and adjusted such that air or hot air may smoothly
flow through the holding pockets 42 to effectively carry out drying and residual droplet
removal.
[0030] It is noted that the flow volume of air or hot air injected from the nozzles in the
drying means and residual droplet removing means may be adjusted as appropriate depending
on the conveying speed of sintered magnet bodies 1, the length of drying zone 3 (the
length of residual droplet removal section), the size and shape of sintered magnet
bodies 1, the concentration and coating weight of the slurry 2 and the like. Although
the flow volume is not particularly limited, it is typically adjusted in a range of
300 to 2,500 L/min, more preferably 500 to 1,800 L/min.
[0031] Though not shown, it is preferred that the drying zone 3 including the residual droplet
removal section be provided with dust collecting means for recovering the rare earth
compound powder removed from the surface of sintered magnet bodies 1 during the residual
droplet removal and drying, by enclosing the dry zone 3 in a suitable chamber and
installing a dust collector in the chamber for collecting dust. This enables coating
of rare earth compound powder without wasting the rare earth compound containing noble
rare earth element. In addition, the provision of the dust collecting means shortens
the drying time, prevents hot air blow from diverting to the slurry coating section
consisting of the coating tank and slurry agitating means as much as possible, and
effectively prevents the slurry solvent from evaporating by the hot air blow. While
the dust collector (not shown) may be of wet or dry type, it is preferred to select
a dust collector having a greater suction capability than the flow volume of air injected
from the nozzles in the residual droplet removing means and drying means.
[0032] As shown in FIG. 1, a range of the conveyor drum 4 corresponding to 2 to 3 o'clock
on the clock dial (range shown by arrow 5 in FIG. 1) is a load/unload zone. In the
load/unload zone 5, an uncoated sintered magnet body 1 is inserted into one holding
pocket 42 and accommodated therein, and a coated sintered magnet body 1 having passed
the immersion and drying steps is displaced from the holding pocket 42 and recovered.
That is, in the load/unload zone 5, the coated sintered magnet body is displaced or
replaced by an uncoated sintered magnet body.
[0033] With respect to the replacement of sintered magnet bodies 1, in one procedure, the
coated sintered magnet body is taken out of the holding pocket 42 and thereafter the
uncoated sintered magnet body is inserted into the holding pocket 42. In another procedure,
the uncoated sintered magnet body is inserted into the holding pocket 42 from one
side surface of the conveyor drum 4, and the coated sintered magnet body accommodated
in the holding pocket 42 is displaced by this uncoated sintered magnet body to the
other side surface of the conveyor drum 4 and recovered, whereby supply and recovery
of sintered magnet bodies 1 are performed at the same time.
[0034] The supply and recovery of sintered magnet bodies 1 may be performed manually or
automatically by providing a suitable supply mechanism and recovery mechanism. In
either case, a support member (not shown) such as a rail is preferably provided so
that the sintered magnet body 1 in a stable attitude may be guided to the holding
pocket 42 or the sintered magnet body 1 in a stable attitude be moved out of the holding
pocket 42.
[0035] Though not shown in FIGS. 1 and 2, the slurry 2 is contained in a box-shaped coating
tank which is open at the upper end, and a portion of the conveyor drum 4 is immersed
in the slurry 2 as mentioned above. The coating tank is equipped with agitating means
(not shown) including a pump and a conduit. The agitating means serves to prevent
precipitation of the rare earth compound in the slurry 2 and to keep the powder uniformly
dispersed in the solvent. Also, the temperature of the slurry 2 may be adjusted as
appropriate in a range of 10 to 40°C, and temperature management means such as a thermometer
and heater may be provided if necessary.
[0036] When the sintered magnet body 1 is coated on its surface with a powder (rare earth
compound powder) containing one or more compounds selected from an oxide, fluoride,
oxyfluoride, hydroxide and hydride of R
2 (wherein R
2 is one or more elements selected from Y, Sc and rare earth elements) using the application
device defined above, first the slurry 2 having the powder dispersed in a solvent
is contained in the coating tank (not shown), and the slurry 2 is appropriately stirred
by the agitating means (not shown) to maintain the powder in the slurry 2 to be uniformly
dispersed in the solvent. In this state, as shown in FIG. 1, the sintered magnet bodies
1 to be treated are conveyed while they are accommodated in the holding pockets 42
in the conveyor drum 4 that rotates with a portion thereof being immersed in the slurry
2.
[0037] As described above, the sintered magnet body 1 which is accommodated in the holding
pocket 42 in the load/unload zone 5 is conveyed forward by rotation of the conveyor
drum 4 while it is held in the pocket 42, introduced into the slurry 2, where the
magnet body is immersed in the slurry 2, passed through the slurry 2 over a predetermined
time, and withdrawn from the slurry 2. In this course, the sintered magnet bodies
1 are successively coated with the slurry 2.
[0038] As the conveyor drum 4 rotates, the sintered magnet body 1 having the slurry 2 applied
thereto is conveyed further and introduced into the drying zone 3 where drying operation
is performed to remove the solvent of the slurry 2, the rare earth compound powder
is tightly deposited on the surface of the sintered magnet body 10, to form a coating
of rare earth compound powder on the surface of the sintered magnet body 10. At this
point, if the drying zone 3 is provided with the residual droplet removal section,
residual droplets are removed from the sintered magnet body 1 as withdrawn from the
slurry 2, before drying treatment is performed on the sintered magnet body.
[0039] The sintered magnet body 1 which has been coated with the rare earth compound powder
as mentioned above is conveyed further to the load/unload zone 5 again. In the load/unload
zone 5, the sintered magnet body 1 coated with the rare earth compound powder is taken
out of the holding pocket 42 and recovered, and the holding pocket 42 is charged with
a new sintered magnet body 1 in the load/unload zone 5. Upon recovery and supply of
sintered magnet bodies 1, a newly supplied uncoated magnet body is inserted into the
holding pocket 42 from one side surface of the conveyor drum 4, and the coated magnet
body which has been accommodated in the holding pocket 42 is displaced by this uncoated
magnet body and recovered, thereby simultaneously performing recovery and supply of
sintered magnet bodies 1. By repeating the series of operations continuously, a multiplicity
of sintered magnet bodies are successively coated with the rare earth compound.
[0040] At this point, the step of coating the rare earth compound using the application
device is repeated plural times on one sintered magnet body to coat the magnet body
with the rare earth compound powder in an overlay manner, whereby a thicker coating
is obtainable and the uniformity of a coating is improved. For repetition of the coating
operation, the magnet body may be fed through one device plural passes to repeat the
coating operation. The repeat operation may include feeding the sintered magnet body
1 to the conveyor drum 4, rotating the drum plural turns rather than one turn, and
thereafter recovering the magnet body. In the case of double coating, for example,
the sintered magnet body 1 is fed to the conveyor drum 4, the drum is rotated two
turns to repeat the operation from slurry immersion to drying two times, and thereafter,
the magnet body is recovered.
[0041] When the conveyor drum 4 having an even number of holding pockets 42 as shown in
FIGS. 1 and 2 is used, in the case of double coating, for example, supply/recovery
of sintered magnet body 1 may be performed every other turn (every two rotations).
When the conveyor drum 4 having an odd number of holding pockets 42 is used, supply/recovery
of sintered magnet body 1 may be performed every other pocket (in alternate pockets).
[0042] In another embodiment, a plurality of conveyor drums 4 are juxtaposed with their
side surfaces closely opposed. The powder coating process is carried out on each conveyor
drum, the sintered magnet body is inserted into the holding pocket in one drum, and
at the same time, the sintered magnet body which has been accommodated in the pocket
is displaced into the pocket in another drum and accommodated therein, whereby the
coating process from slurry immersion to drying is repeated plural times.
[0043] In the case of double coating, for example, as shown in FIG. 3, two conveyor drums
4a and 4b similar to the conveyor drum 4 are juxtaposed and rotated synchronously
with the holding pockets 42 in the two drums 4a and 4b being aligned with each other.
On each of the conveyor drums 4a and 4b, the coating process from slurry immersion
to drying is carried out. The sintered magnet body which has undergone the first coating
treatment on the first conveyor drum 4a is transferred to the second conveyor drum
4b where it undergoes the second coating treatment. Specifically, an uncoated sintered
magnet body 1a is inserted and supplied into one holding pocket 42a in the first conveyor
drum 4a. By this uncoated magnet body 1a, the once coated magnet body 1a which has
been accommodated in the holding pocket 42a is displaced, transferred and inserted
into the holding pocket 42b in the second conveyor drum 4b. By the once coated sintered
magnet body 1a, the twice coated sintered magnet body 1c which has been accommodated
in the holding pocket 42b is displaced and recovered. In FIG. 3, the slurry 2 is contained
in a coating tank t.
[0044] In a further embodiment, the juxtaposition of plural conveyor drums as shown in FIG.
3 may be combined with the overlay coating by rotating the conveyor drum plural turns.
For example, in the device shown in FIG. 3, overlay coating of four layers is possible
by performing supply and recovery of sintered magnet bodies on every two turns. It
is noted that the method of FIG. 3 using a plurality of conveyor drums has a throughput
which is twice that of the method of rotating a single conveyor drum with the sintered
magnet body plural turns, provided that the conditions are the same, and is advantageous
in process efficiency. On the other hand, the method of rotating the conveyor drum
plural times is advantageous in that the device is made simple and compact. By combining
both methods, naturally overlay coating of 4 or more layers is possible. Efficient
overlay coating with the advantages of both methods is possible.
[0045] In this way, the powder coating process from slurry application to drying is repeated
plural times to achieve overlay coating of thin layers until a coating of desired
thickness is reached. The overlay coating of thin layers is effective for reducing
the drying time whereby the time-basis efficiency is improved.
[0046] In the inventive method for coating a sintered magnet body with a rare earth compound
powder using the application device as mentioned above, as the sintered magnet body
1 is conveyed by the conveyor drum 4 while it is accommodated in the holding pocket
42 in the drum 4, it is subjected to slurry coating and drying. Even when coating
step is continuously performed on a plurality of sintered magnet bodies 1, it is avoided
that sintered magnet bodies come in contact with each other so that coating defects
form at the contact areas. The slurry 2 can be uniformly and properly applied, and
the powder be uniformly and efficiently coated. Since the conveyor drum 1 rotates
while a portion thereof is immersed in the slurry 2 in the coating tank, the slurry
2 carried over by the conveyor drum 1 is returned to the coating tank due to rotation
of the drum 1, and little of the slurry is carried out of the coating tank. The wasting
of rare earth compound is suppressed quite effectively, as compared with the net conveyor
system. Further, since the conveyance track of the sintered magnet body 1 by the conveyor
drum 4 is a circular track about the horizontal axis extending above the coating tank,
the device is made compact and the footprint of the device is substantially reduced,
as compared with the net conveyor system entailing a horizontal conveyance track.
[0047] Accordingly, the sintered magnet body is coated on its surface with the rare earth
compound powder uniformly and efficiently. The sintered magnet body uniformly coated
with the powder is heat treated to cause absorptive diffusion of the rare earth element
R
2 whereby a rare earth magnet having a fully increased coercivity and improved magnetic
properties is efficiently produced.
[0048] Notably, the heat treatment to cause absorptive diffusion of the rare earth element
R
2 may be performed by a well-known method. After the heat treatment, any well-known
post-treatments including aging treatment under suitable conditions and machining
to a practical shape may be performed, if necessary.
EXAMPLE
[0049] Embodiments of the invention are described by referring to Example although the invention
is not limited thereto.
[Example]
[0050] A thin plate of alloy was prepared by a so-called strip casting technique, specifically
by weighing amounts of Nd, Al, Fe and Cu metals having a purity of at least 99 wt%,
Si having a purity of 99.99 wt%, and ferroboron, high-frequency heating in argon atmosphere
for melting, and casting the alloy melt on a copper single roll in argon atmosphere.
The resulting alloy consisted of 14.5 at% Nd, 0.2 at% Cu, 6.2 at% B, 1.0 at% Al, 1.0
at% Si, and the balance of Fe. The alloy was exposed to 0.11 MPa of hydrogen at room
temperature for hydriding, and then heated at 500°C for partial dehydriding while
evacuating to vacuum. It is cooled and sieved, obtaining a coarse powder having a
size of up to 50 mesh.
[0051] On a jet mill using high-pressure nitrogen gas, the coarse powder was finely pulverized
to a weight cumulative median particle size of 5 µm. The resulting fine powder was
compacted in a nitrogen atmosphere under a pressure of about 1 ton/cm
2 while being oriented in a magnetic field of 15 kOe. The compact was then placed in
a sintering furnace in argon atmosphere where it was sintered at 1,060°C for 2 hours,
obtaining a magnet block. Using a diamond cutter, the magnet block was machined on
all the surfaces, cleaned with alkaline solution, pure water, nitric acid and pure
water in sequence, and dried, obtaining a block-shaped magnet body of 50 mm × 20 mm
× 5 mm (in magnetic anisotropy direction).
[0052] Next, dysprosium fluoride powder was mixed with water at a mass fraction of 40 %
and thoroughly dispersed therein to form a slurry. Using the application device shown
in FIGS. 1 and 2, the slurry was applied to the magnet body and dried, forming a coating
of dysprosium fluoride powder. The coating conditions are shown below.
Coating conditions
Coating tank volume: |
10 L |
Circulating flow rate of slurry: |
60 L/min |
Conveying speed: |
700 mm/min |
Flow volume of air for droplet removal and drying: |
1,000 L/min |
Temperature of hot air for drying: |
80°C |
Coating number: |
single coating |
Number of block-shaped magnet bodies: |
100 |
[0053] The slurry spilling from the coating tank during treatment of 100 magnet bodies was
collected, dried and weighed, which value is reported as the carry-over of slurry
from the coating tank. Also the number of block-shaped magnet bodies which were brought
in surface contact after coating was counted. The results are shown in Table 1.
[0054] The magnet bodies having a thin coating of dysprosium fluoride powder formed on their
surface were heat treated at 900°C for 5 hours in Ar atmosphere for absorptive treatment,
age treated at 500°C for 1 hour, and quenched, obtaining rare earth magnet samples.
All magnet samples had satisfactory magnetic properties.
[Comparative Example]
[0055] As in Example, there was furnished a block-shaped magnet body of 50 mm × 20 mm ×
5 mm (in magnetic anisotropy direction). Also, dysprosium fluoride powder having an
average particle size of 0.2 µm was mixed with water at a mass fraction of 40 % and
thoroughly dispersed therein to form a slurry, which was contained in a coating tank
t of the prior art coating system shown in FIG. 4. The magnet body was coated with
dysprosium fluoride by using the prior art coating system, and adjusting the conveying
speed of net conveyor
c, the residual droplet removing and drying conditions in drying zone 3, and the like
so as to establish coating conditions equivalent to those of Example 1. The specifications
of a net belt used in net conveyor
c are as follows.
<Net belt specifications>
Type: |
conveyor belt |
Form: |
triangular spiral |
Spiral pitch: |
8.0 mm |
Rod pitch: |
10.2 mm |
Rod gauge: |
1.5 mm |
Spiral gauge: |
1.2 mm |
[0056] As in Example, the carry-over of the slurry from the coating tank was measured. Also
the number of block-shaped magnet bodies which exited the drying zone 3 in mutual
surface contact state after coating was counted. The results are shown in Table 1.
It is noted that the slurry carry-over is reported as an index provided that the carry-over
of Example 1 is 1.
[0057] As in Example, the magnet bodies having a thin coating of dysprosium fluoride powder
formed on their surface were heat treated at 900°C for 5 hours in Ar atmosphere for
absorptive treatment, age treated at 500°C for 1 hour, and quenched, obtaining rare
earth magnet samples.
[Table 1]
|
Slurry carry-over from coating tank (index based on 1 for Example) |
Number of magnet bodies exiting in surface contact |
Example |
1 |
0 |
Comparative Example |
9.19 |
1 |
[0058] As is evident from Table 1, a comparison of slurry carry-over from the coating tank
reveals that the carry-over of the application device comprising a rotating drum is
about 89 % smaller than that of the net conveyor system of serial movement. As is
also evident from Table 1, the number of block-shaped magnet bodies which exited in
mutual surface contact after coating is nil in the rotary drum pocket system of the
invention (Example), demonstrating effective coating of powder.
REFERENCE SIGNS LIST
[0059]
- 1
- sintered magnet body
- 1a
- uncoated sintered magnet body
- 1b
- once coated sintered magnet body
- 1c
- twice coated sintered magnet body
- 2
- slurry
- 3
- drying zone
- 4
- conveyor drum
- 4a
- first conveyor drum
- 4b
- second conveyor drum
- 41
- horizontal axis
- 42
- holding pocket
- 42a
- holding pocket in first conveyor drum
- 42b
- holding pocket in second conveyor drum
- 5
- load/unload zone
- c
- net conveyor
- t
- coating tank
1. A method for producing rare earth permanent magnet comprising the steps of applying
a slurry (2) of a powder in a solvent to sintered magnet bodies (1) of R
1-Fe-B composition, wherein R
1 is one or more elements selected from Y, Sc and rare earth elements, the powder containing
one or more compounds selected from an oxide, fluoride, oxyfluoride, hydroxide and
hydride of R
2, wherein R
2 is one or more elements selected from Y, Sc and rare earth elements, drying the slurry
(2) to coat the sintered magnet bodies (1) with the powder, and heat treating the
coated bodies (1b, 1c) for causing R
2 to be absorbed in the sintered magnet bodies (1), the method
characterized in that it further comprises the steps of:
providing a conveyor drum (4) having a plurality of holding pockets (42) circumferentially
arranged in its periphery,
rotating the conveyor drum (4) while a portion of the drum is immersed in the slurry
(2),
placing a sintered magnet body (1) in one holding pocket (42) at a predetermined position
of the drum (4) prior to entry into the slurry (2), so that the sintered magnet body
(1) is held in the holding pocket (42), the sintered magnet body (1) being conveyed
along the rotational track of the conveyor drum (4), immersed in the slurry (2), then
withdrawn from the slurry (2), and conveyed further whereby the slurry (2) is dried
and the sintered magnet body (1) is coated with the powder,
recovering the sintered magnet body (1) from the pocket (42) at a predetermined position
after the drying treatment and prior to re-entry into the slurry (2), and
subjecting the sintered magnet body (1) to the subsequent heat treatment.
2. The rare earth magnet producing method of claim 1 wherein the holding pocket (42)
is a pocket of circular bore shape axially extending throughout the conveyor drum
(4), an uncoated sintered magnet body (1a) is inserted into the pocket (42) from one
side surface of the conveyor drum (4), a coated sintered magnet body (1b, 1c), which
has been accommodated in the pocket (42), is displaced by the uncoated sintered magnet
body (1a) to the other side surface of the conveyor drum (4), for thereby recovering
the coated sintered magnet body (1b, 1c) from the pocket (42), whereby supply and
recovery of sintered magnet bodies are simultaneously performed.
3. The rare earth magnet producing method of claim 2 wherein a plurality of conveyor
drums (4a, 4b) are juxtaposed with their side surfaces closely opposed, the powder
coating process is carried out on each conveyor drum (4a, 4b), the sintered magnet
body (1) is inserted into the holding pocket (42a) in one drum, and at the same time,
the sintered magnet body (1), which has been accommodated in the pocket (42a), is
displaced into the pocket (42b) in another drum (4b) and accommodated therein, whereby
the coating process from slurry immersion to drying is repeated plural times.
4. The rare earth magnet producing method of any one of claims 1 to 3 wherein the sintered
magnet body (1) supplied into the holding pocket (42) is recovered after the conveyor
drum (4) is rotated plural turns, whereby the coating process from slurry immersion
to drying is repeated plural times.
5. The rare earth magnet producing method of any one of claims 1 to 4 wherein the conveyor
drum (4) has a main body composed of a frame and a mesh metal or punching metal.
6. The rare earth magnet producing method of any one of claims 1 to 5 wherein the step
of drying the sintered magnet body (1) which is withdrawn from the slurry (2) and
conveyed further includes blowing air thereto.
7. The rare earth magnet producing method of claim 6 wherein the drying step includes
injecting air at a temperature within the boiling point (TB) of the solvent in the slurry (2) ±50°C to the sintered magnet body (1).
8. The rare earth magnet producing method of claim 6 or 7 wherein the drying step includes
injecting air to the sintered magnet body (1) which is withdrawn from the slurry (2),
for thereby removing any residual droplets, and then injecting hot air thereto.
9. A device for applying rare earth compound when rare earth permanent magnet is produced
by applying a slurry (2) of a powder in a solvent to sintered magnet bodies (1) of
R1-Fe-B composition, wherein R1 is one or more elements selected from Y, Sc and rare earth elements, the powder containing
one or more compounds selected from an oxide, fluoride, oxyfluoride, hydroxide and
hydride of R2, wherein R2 is one or more elements selected from Y, Sc and rare earth elements, drying the slurry
(2) to coat the sintered magnet bodies (1) with the powder, and heat treating the
coated bodies (1b, 1c) for causing R2 to be absorbed in the sintered magnet bodies (1),
characterized in that the device comprises
an applicator tank (t) for containing the slurry (2),
a conveyor drum (4) which rotates while a portion of the drum (4) is immersed in the
slurry (2),
a plurality of holding pockets (42) circumferentially arranged in the periphery of
the conveyor drum (4), and
drying means for blowing air into the holding pocket (42) for drying the sintered
magnet body (1) accommodated in the pocket (42),
wherein a sintered magnet body (1) is supplied into one holding pocket (42) at a predetermined
position of the drum (4) prior to entry into the slurry (2), the sintered magnet body
(1) held in the pocket (42) is conveyed along the rotational track of the conveyor
drum (4), immersed in the slurry (2), then withdrawn from the slurry (2), and dried
by the drying means, and the sintered magnet body (1) is recovered from the pocket
(42) at a predetermined position after the drying treatment and prior to re-entry
into the slurry (2).
10. The rare earth compound application device of claim 9 wherein the conveyor drum (42)
has a main body composed of a frame and a mesh metal or punching metal.
11. The rare earth compound application device of claim 9 or 10 wherein the drying means
is adapted to blow hot air into the holding pocket (42) to dry the sintered magnet
body (1) therein, the device further comprising droplet removing means for injecting
air to the sintered magnet body (1) accommodated in the pocket (42) for thereby removing
any residual droplets, prior to the drying treatment.
12. The rare earth compound application device of any one of claims 9 to 11 wherein the
holding pocket (42) is a pocket of circular bore shape axially extending throughout
the conveyor drum (4), an uncoated sintered magnet body (1a) is inserted into the
pocket (42) from one side surface of the conveyor drum (4), a coated sintered magnet
body (1b, 1c), which has been accommodated in the pocket (42), is displaced by the
uncoated sintered magnet body (1a) to the other side surface of the conveyor drum
(4), for thereby recovering the coated sintered magnet body (1b, 1c) from the pocket
(42).
13. The rare earth compound application device of claim 12 wherein a plurality of conveyor
drums (4a, 4b) are juxtaposed with their side surfaces closely opposed, the powder
coating process is carried out on each conveyor drum (4a, 4b), the sintered magnet
body (1) is inserted into the holding pocket (42a) in one drum (4a), and at the same
time, the sintered magnet body (1), which has been accommodated in the pocket (42a),
is displaced into the pocket (42b) in another drum (4b) and accommodated therein,
whereby the coating process from slurry immersion to drying is repeated plural times.
14. The rare earth compound application device of any one of claims 9 to 13 wherein the
sintered magnet body (1) supplied into the holding pocket (42) is recovered after
the conveyor drum (4) is rotated plural turns, whereby the coating process from slurry
immersion to drying is repeated plural times.
1. Verfahren zur Herstellung von Seltenerdpermanentmagneten, wobei das Verfahren folgende
Schritte umfasst: das Aufbringen einer Aufschlämmung (2) von einem Pulver in einem
Lösungsmittel auf Magnetsinterkörpern (1) aus einer R
1-Fe-B-Zusammensetzung, worin R
1 ein aus Y, Sc und Seltenerdelementen ausgewähltes Element oder mehrere aus diesen
ausgewählte Elemente ist, wobei das Pulver ein oder mehrere Verbindungen ausgewählt
aus einem Oxid, Fluorid, Oxyfluorid, Hydroxid und Hydrid von R
2 enthält, wobei R
2 ein oder mehrere Elemente ausgewählt aus Y, Sc und Seltenerdelementen ist, das Trocknen
der Aufschlämmung (2) zur Beschichtung der Magnetsinterkörper (1) mit dem Pulver und
das Wärmebehandeln der beschichteten Körper (1b, 1c), um zu bewirken, dass R
2 in die Magnetsinterkörper (1) absorbiert wird, wobei das Verfahren
dadurch gekennzeichnet ist, dass es ferner folgende Schritte umfasst:
das Bereitstellen einer Fördertrommel (4) mit einer Vielzahl von Haltefächern (42),
die in ihrem Randbereich umlaufend angeordnet sind,
das Drehen der Fördertrommel (4), während ein Abschnitt der Trommel in die Aufschlämmung
(2) eingetaucht ist,
das Platzieren eines Magnetsinterkörpers (1) in einem Haltefach (42) an einer vorbestimmten
Position der Trommel (4) vor dem Eintritt in die Aufschlämmung (2), so dass der Magnetsinterkörper
(1) in dem Haltefach (42) gehalten wird, wobei der Magnetsinterkörper (1) entlang
der Rotationsspur der Fördertrommel (4) bewegt wird, in die Aufschlämmung (2) eingetaucht
und dann aus der Aufschlämmung (2) gezogen wird und dann weiter bewegt wird, wodurch
die Aufschlämmung (2) getrocknet wird und der Magnetsinterkörper (1) mit dem Pulver
beschichtet wird,
das Entnehmen des Magnetsinterkörpers (1) aus dem Fach (42) an einer vorbestimmten
Position nach der Trockenbehandlung und vor dem erneuten Eintritt in die Aufschlämmung
(2) und
das Aussetzen des Magnetsinterkörpers (1) gegenüber der nachfolgenden Wärmebehandlung.
2. Verfahren zur Herstellung von Seltenerdmagneten nach Anspruch 1, wobei das Haltefach
(42) ein Fach mit einer kreisförmigen Durchgangslochform ist, die sich axial durch
die Fördertrommel (4) erstreckt, ein unbeschichteter Magnetsinterkörper (1a) von einer
Seitenoberfläche der Fördertrommel (4) aus in das Fach (42) eingebracht wird, ein
beschichteter Magnetsinterkörper (1b, 1c), der in dem Fach (42) aufgenommen war, durch
den unbeschichteten Magnetsinterkörper (1a) zu der anderen Seitenoberfläche der Fördertrommel
(4) verschoben wird, um dadurch den beschichteten Magnetsinterkörper (1b, 1c) aus
dem Fach (42) zu entnehmen, wodurch Zufuhr und Entnahme der Magnetsinterkörper gleichzeitig
durchgeführt werden.
3. Verfahren zur Herstellung von Seltenerdmagneten nach Anspruch 2, wobei eine Vielzahl
von Fördertrommeln (4a, 4b) mit ihren Seitenoberflächen nahe gegenüberliegend nebeneinander
angeordnet sind, das Pulverbeschichtungsverfahren auf jeder Fördertrommel (4a, 4b)
durchgeführt wird, der Magnetsinterkörper (1) in das Haltefach (42a) in einer Trommel
eingebracht wird und gleichzeitig der Magnetsinterkörper (1), der in dem Fach (42a)
aufgenommen war, in das Fach (42b) in einer anderen Trommel (4b) verschoben und darin
aufgenommen wird, wodurch das Beschichtungsverfahren vom Eintauchen in die Aufschlämmung
bis zum Trocknen mehrmals wiederholt wird.
4. Verfahren zur Herstellung von Seltenerdmagneten nach einem der Ansprüche 1 bis 3,
wobei der Magnetsinterkörper (1), der in das Haltefach (42) zugeführt wird, wieder
entnommen wird, nachdem die Fördertrommel (4) mehrere Umdrehungen gedreht wurde, wodurch
das Beschichtungsverfahren vom Eintauchen in die Aufschlämmung bis zum Trocknen mehrmals
wiederholt wird.
5. Verfahren zur Herstellung von Seltenerdmagneten nach einem der Ansprüche 1 bis 4,
wobei die Fördertrommel (4) einen Hauptkörper aufweist, der aus einem Rahmen und einem
Metallnetz oder einem Lochmetall besteht.
6. Verfahren zur Herstellung von Seltenerdmagneten nach einem der Ansprüche 1 bis 5,
wobei der Schritt des Trocknens des Magnetsinterkörpers (1), der aus der Aufschlämmung
(2) herausgezogen und weiterbewegt wird, das Aufblasen von Luft auf diesen umfasst.
7. Verfahren zur Herstellung von Seltenerdmagneten nach Anspruch 6, wobei der Schritt
des Trocknens das Einblasen von Luft bei einer Temperatur innerhalb des Siedepunkts
(TB) des Lösungsmittels in der Aufschlämmung (2) ±50 °C auf den Magnetsinterkörper (1)
umfasst.
8. Verfahren zur Herstellung von Seltenerdmagneten nach Anspruch 6 oder 7, wobei der
Schritt des Trocknens das Einblasen von Luft auf den Magnetsinterkörper (1) umfasst,
der aus der Aufschlämmung (2) herausgezogen wird, um dadurch etwaige verbleibende
Tröpfchen zu entfernen, wonach Heißluft auf diesen eingeblasen wird.
9. Vorrichtung zum Aufbringen einer Seltenderdverbindung bei Herstellung eines Seltenerdpermanentmagneten
durch Aufbringen einer Aufschlämmung (2) aus einem Pulver in einem Lösungsmittel auf
Magnetsinterkörper (1) aus einer R
1-Fe-B-Zusammensetzung, worin R
1 ein aus Y, Sc und Seltenerdelementen ausgewähltes Element oder mehrere aus diesen
ausgewählte Elemente ist, wobei das Pulver ein oder mehrere Verbindungen ausgewählt
aus einem Oxid, Fluorid, Oxyfluorid, Hydroxid und Hydrid von R
2 enthält, wobei R
2 ein oder mehrere Elemente ausgewählt aus Y, Sc und Seltenerdelementen ist, das Trocknen
der Aufschlämmung (2) zur Beschichtung der Magnetsinterkörper (1) mit dem Pulver und
das Wärmebehandeln der beschichteten Körper (1b, 1c), um zu bewirken, dass R
2 in die Magnetsinterkörper (1) absorbiert wird,
dadurch gekennzeichnet, dass die Vorrichtung Folgendes umfasst:
einen Applikatorbehälter (t) zur Aufnahme der Aufschlämmung (2),
eine Fördertrommel (4) die sich dreht, während ein Abschnitt der Trommel (4) in die
Aufschlämmung (2) eingetaucht ist,
eine Vielzahl von Haltefächern (42), die im Randbereich der Fördertrommel (4) umlaufend
angeordnet ist, und
Trockenmittel zum Einblasen von Luft in das Haltefach (42) zum Trocknen des Magnetsinterkörpers
(1), der in dem Fach (42) aufgenommen ist,
wobei ein Magnetsinterkörper (1) in ein Haltefach (42) an einer vorbestimmten Position
der Trommel (4) vor dem Eintritt in die Aufschlämmung (2) zugeführt wird, der in dem
Fach gehaltene Magnetsinterkörper (1) entlang dem Rotationspfad der Fördertrommel
(4) transportiert wird, in die Aufschlämmung (2) eingetaucht wird, dann aus der Aufschlämmung
(2) herausgezogen wird und durch die Trockenmittel getrocknet wird und der Magnetsinterkörper
(1) aus dem Fach (42) an einer vorbestimmten Position nach der Trockenbehandlung und
vor dem erneuten Eintritt in die Aufschlämmung (2) entnommen wird.
10. Vorrichtung zum Aufbringen einer Seltenerdverbindung nach Anspruch 9, wobei die Fördertrommel
(42) einen Hauptkörper aufweist, der aus einem Rahmen und einem Metallnetz oder einem
Lochmetall besteht.
11. Vorrichtung zum Aufbringen einer Seltenerdverbindung nach Anspruch 9 oder 10, wobei
das Trockenmittel geeignet ist, um Heißluft in das Haltefach (42) einzublasen, um
den Magnetsinterkörper (1) darin zu trocknen, die Vorrichtung ferner Tröpfchenentfernungsmittel
zum Einblasen von Luft in den in dem Fach (42) aufgenommenen Magnetsinterkörper (1)
umfasst, um dadurch etwaige verbleibende Tröpfchen vor der Trockenbehandlung zu entfernen.
12. Vorrichtung zum Aufbringen einer Seltenerdverbindung nach einem der Ansprüche 9 bis
11, wobei das Haltefach (42) ein Fach in der Form eines kreisförmigen Durchgangslochs
ist, das sich durch die Fördertrommel (4) axial erstreckt, ein unbeschichteter Magnetsinterkörper
(1a) von einer Seitenoberfläche der Fördertrommel (4) aus in das Fach (42) eingebracht
wird, ein beschichteter Magnetsinterkörper (1b, 1c), der in dem Fach (42) aufgenommen
war, wird durch den unbeschichteten Magnetsinterkörper (1a) zu der anderen Seitenoberfläche
der Fördertrommel (4) verschoben wird, um dadurch den beschichteten Magnetsinterkörper
(1b, 1c) aus dem Fach (42) zu entnehmen.
13. Vorrichtung zum Aufbringen einer Seltenerdverbindung nach Anspruch 12, wobei eine
Vielzahl von Fördertrommeln (4a, 4b) mit ihren Seitenoberflächen nahe gegenüberliegend
nebeneinander angeordnet sind, das Pulverbeschichtungsverfahren auf jeder Fördertrommel
(4a, 4b) durchgeführt wird, der Magnetsinterkörper (1) in das Haltefach (42a) in einer
Trommel (4a) eingebracht wird und gleichzeitig der Magnetsinterkörper (1), der in
dem Fach (42a) aufgenommen war, in das Fach (42b) in einer anderen Trommel (4b) verschoben
und darin aufgenommen wird, wodurch das Beschichtungsverfahren vom Eintauchen in die
Aufschlämmung bis zum Trocknen mehrmals wiederholt wird.
14. Vorrichtung zum Aufbringen einer Seltenerdverbindung nach einem der Ansprüche 9 bis
13, wobei der Magnetsinterkörper (1), der in das Haltefach (42) zugeführt wird, wieder
entnommen wird, nachdem die Fördertrommel (4) mehrere Umdrehungen gedreht wurde, wodurch
das Beschichtungsverfahren vom Eintauchen in die Aufschlämmung bis zum Trocknen mehrmals
wiederholt wird.
1. Procédé de fabrication d'aimant permanent aux terres rares comprenant les étapes d'application
d'une suspension épaisse (2) d'une poudre dans un solvant à des corps d'aimant frittés
(1) de composition R
1-Fe-B, dans lequel R
1 représente un ou plusieurs éléments choisis parmi Y, Sc et des éléments des terres
rares, la poudre contenant un ou plusieurs composés choisis parmi un oxyde, un fluorure,
un oxyfluorure, un hydroxyde et un hydrure de R
2, dans lequel R
2 représente un ou plusieurs éléments choisis parmi Y, Sc et des éléments des terres
rares, de séchage de la suspension épaisse (2) pour revêtir les corps d'aimant frittés
(1) avec la poudre, et de traitement thermique des corps revêtus (1b, 1c) pour amener
R
2 à être absorbé dans les corps d'aimant frittés (1), le procédé étant
caractérisé en ce qu'il comprend en outre les étapes de :
fourniture d'un tambour de transport (4) comportant une pluralité de poches de maintien
(42) agencées de façon circonférentielle dans sa périphérie,
rotation du tambour de transport (4) alors qu'une partie du tambour est immergée dans
la suspension épaisse (2),
mise en place d'un corps d'aimant fritté (1) dans une poche de maintien (42) à un
emplacement prédéterminé du tambour (4) avant entrée dans la suspension épaisse (2),
de sorte que le corps d'aimant fritté (1) est maintenu dans la poche de maintien (42),
le corps d'aimant fritté (1) étant transporté le long de la piste rotative du tambour
de transport (4), immergé dans la suspension épaisse (2), puis extrait de la suspension
épaisse (2) et transporté plus loin, moyennant quoi la suspension épaisse (2) est
séchée et le corps d'aimant fritté (1) est revêtu avec la poudre,
récupération du corps d'aimant fritté (1) de la poche (42) à un emplacement prédéterminé
après le traitement de séchage et avant nouvelle entrée dans la suspension épaisse
(2), et
soumission du corps d'aimant fritté (1) au traitement thermique suivant.
2. Procédé de fabrication d'aimant aux terres rares selon la revendication 1, dans lequel
la poche de maintien (42) est une poche en forme d'alésage circulaire s'étendant axialement
d'un bord à l'autre du tambour de transport (4), un corps d'aimant fritté non revêtu
(1a) est inséré dans la poche (42) à partir d'une première surface latérale du tambour
de transport (4), un corps d'aimant fritté revêtu (1b, 1c) qui logeait dans la poche
(42) est déplacé par le corps d'aimant fritté non revêtu (1a) jusqu'à l'autre surface
latérale du tambour de transport (4), permettant ainsi de récupérer le corps d'aimant
fritté revêtu (1b, 1c) de la poche (42), moyennant quoi la fourniture et la récupération
des corps d'aimant frittés s'effectuent simultanément.
3. Procédé de fabrication d'aimant aux terres rares selon la revendication 2, dans lequel
une pluralité de tambours de transport (4a, 4b) sont juxtaposés avec leurs surfaces
latérales en étroite opposition, le processus de revêtement de poudre est effectué
sur chaque tambour de transport (4a, 4b), le corps d'aimant fritté (1) est inséré
dans la poche de maintien (42a) d'un premier tambour et, en même temps, le corps d'aimant
fritté (1) qui logeait dans la poche (42a) est déplacé dans la poche (42b) d'un autre
tambour (4b) et logé dans celle-ci, moyennant quoi le processus de revêtement depuis
l'immersion dans la suspension épaisse jusqu'au séchage est répété à plusieurs reprises.
4. Procédé de fabrication d'aimant aux terres rares selon l'une quelconque des revendications
1 à 3, dans lequel le corps d'aimant fritté (1) fourni dans la poche de maintien (42)
est récupéré après que le tambour de transport (4) a effectué plusieurs tours, moyennant
quoi le processus de revêtement depuis l'immersion dans la suspension épaisse jusqu'au
séchage est répété à plusieurs reprises.
5. Procédé de fabrication d'aimant aux terres rares selon l'une quelconque des revendications
1 à 4, dans lequel le tambour de transport (4) possède un corps principal composé
d'un bâti et d'un grillage métallique ou d'un métal de poinçonnage.
6. Procédé de fabrication d'aimant aux terres rares selon l'une quelconque des revendications
1 à 5, dans lequel l'étape de séchage du corps d'aimant fritté (1) qui a été extrait
de la suspension épaisse (2) et transporté plus loin comprend le soufflage d'air sur
celui-ci.
7. Procédé de fabrication d'aimant aux terres rares selon la revendication 6, dans lequel
l'étape de séchage inclut l'envoi d'un jet d'air à une température inférieure au point
d'ébullition (TB) du solvant dans la suspension épaisse (2) ± 50 °C sur le corps d'aimant fritté (1).
8. Procédé de fabrication d'aimant aux terres rares selon les revendications 6 ou 7,
dans lequel l'étape de séchage inclut l'envoi d'un jet d'air sur le corps d'aimant
fritté (1) qui a été extrait de la suspension épaisse (2), permettant ainsi d'éliminer
d'éventuelles gouttelettes résiduelles, puis l'envoi d'un jet d'air chaud sur celui-ci.
9. Dispositif d'application de composé aux terres rares lors de la fabrication d'un aimant
permanent aux terres rares par application d'une suspension épaisse (2) d'une poudre
dans un solvant à des corps d'aimant frittés (1) de composition R1-Fe-B, dans lequel R1 représente un ou plusieurs éléments choisis parmi Y, Sc et des éléments des terres
rares, la poudre contenant un ou plusieurs éléments choisis parmi un oxyde, un fluorure,
un oxyfluorure, un hydroxyde et un hydrure de R2, dans lequel R2 représente un ou plusieurs éléments choisis parmi Y, Sc et des éléments des terres
rares, séchage de la suspension épaisse (2) pour revêtir les corps d'aimant frittés
(1) avec la poudre, et traitement thermique des corps revêtus (1b, 1c) pour amener
le R2 à être absorbé dans les corps d'aimant frittés (1),
caractérisé en ce que le dispositif comprend
un réservoir d'application (t) destiné à contenir la suspension épaisse (2),
un tambour de transport (4) qui tourne alors qu'une partie du tambour est immergée
dans la suspension épaisse (2),
une pluralité de poches de maintien (42) agencées de façon circonférentielle dans
la périphérie du tambour de transport (4), et
un moyen de séchage pour souffler de l'air dans la poche de maintien (42) afin de
sécher le corps d'aimant fritté (1) logé dans la poche (42),
dans lequel un corps d'aimant fritté (1) est fourni dans une poche de maintien (42)
à un emplacement prédéterminé du tambour (4) avant entrée dans la suspension épaisse
(2), le corps d'aimant fritté (1) retenu dans la poche (42) est transporté le long
de la piste rotative du tambour de transport (4), immergé dans la suspension épaisse
(2), puis extrait de la suspension épaisse (2) et séché par le moyen de séchage, et
le corps d'aimant fritté (1) est récupéré de la poche (42) à un emplacement prédéterminé
après le traitement de séchage et avant nouvelle entrée dans la suspension épaisse
(2).
10. Dispositif d'application de composé aux terres rares selon la revendication 9, dans
lequel le tambour de transport (42) possède un corps principal composé d'un bâti et
d'un grillage métallique ou d'un métal de poinçonnage.
11. Dispositif d'application de composé aux terres rares selon les revendications 9 ou
10, dans lequel le moyen de séchage est apte à souffler de l'air chaud dans la poche
de maintien (42) pour sécher le corps d'aimant fritté (1) dans celle-ci, le dispositif
comprenant en outre un moyen d'élimination de gouttelettes destiné à envoyer un jet
d'air sur le corps d'aimant fritté (1) logé dans la poche (42), permettant ainsi d'éliminer
d'éventuelles gouttelettes résiduelles, avant le traitement de séchage.
12. Dispositif d'application de composé aux terres rares selon l'une quelconque des revendications
9 à 11, dans lequel la poche de maintien (42) est une poche en forme d'alésage circulaire
s'étendant axialement d'un bord à l'autre du tambour de transport (4), un corps d'aimant
fritté non revêtu (1a) est inséré dans la poche (42) à partir d'une première surface
latérale du tambour de transport (4), un corps d'aimant fritté revêtu (1b, 1c) qui
logeait dans la poche (42) est déplacé par le corps d'aimant fritté non revêtu (1a)
jusqu'à l'autre surface latérale du tambour de transport (4), permettant ainsi de
récupérer le corps d'aimant fritté revêtu (1b, 1c) de la poche (42).
13. Dispositif d'application de composé aux terres rares selon la revendication 12, dans
lequel une pluralité de tambours de transport (4a, 4b) sont juxtaposés avec leurs
surfaces latérales en étroite opposition, le processus de revêtement de poudre est
effectué sur chaque tambour de transport (4a, 4b), le corps d'aimant fritté (1) est
inséré dans la poche de maintien (42a) d'un premier tambour (4a) et, en même temps,
le corps d'aimant fritté (1) qui logeait dans la poche (42a) est déplacé dans la poche
(42b) d'un autre tambour (4b) et logé dans celle-ci, moyennant quoi le processus de
revêtement depuis l'immersion dans la suspension épaisse jusqu'au séchage est répété
à plusieurs reprises.
14. Dispositif d'application de composé aux terres rares selon l'une quelconque des revendications
9 à 13, dans lequel le corps d'aimant fritté (1) fourni dans la poche de maintien
(42) est récupéré après que le tambour de transport (4) a effectué plusieurs tours,
moyennant quoi le processus de revêtement depuis l'immersion dans la suspension épaisse
jusqu'au séchage est répété à plusieurs reprises.